The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Apparatus are employed as continuously blending mixers, in which sand, sand-like particles, or other particulate solids are mixed (or blended) with a gel or slickwater composition, and the resulting slurry is pressurized by the mixer itself. A typical use for the resulting slurry is as a treating fluid, which is introduced into a well to enhance recovery of a petroleum product. The blending mixers typically have has a slinger element of a toroidal configuration with a concave upper surface. Several upstanding blade members are mounted on the concave surface of this slinger and an impeller member is attached to the underside of the slinger. The slinger and the impeller are enclosed within a housing and fastened to the end of a drive shaft rotated by a motor mounted above the housing. A hopper is mounted above an inlet eye in the top of the housing, for introducing sand or the other sand-like particles into the housing. At the bottom of the housing is a suction eye inlet, for drawing liquid into the housing, and the resulting liquid-solid mixture is discharged through an outlet port in the housing.
In a continuous blending operation the objective is to be able to prepare a slurry of particulate material (such as sand or other propping agents) and liquid (the gel composition, or other liquid, such as water) and pressurizing the resulting slurry to a desired level. In the operation of the blending mixer, sand flows out of the hopper in a continuous stream and drops onto the rotating slinger through the inlet eye in the housing. With the impeller and slinger rotating at the same speed, the vortex action of the impeller creates a suction force that draws the gel composition into the casing through the suction eye inlet. As the gel is pulled into the mixing casing it is pressurized by the impeller and it mixes thoroughly with the sand being flung outwardly, in a centrifugal action, from the slinger. The sand-gel mixture is then continuously discharged, under pressure, through the outlet port, from which it is carried into a pumper unit and injected into a well.
The structure of the mixing impeller can create a significant resistance in the flow of solids, and the large surface area of the impeller which also has a very close fit within the mixing casing contributes to frictional drag and erosion of the impeller and other parts of the blending mixer. Further, the liquid composition can become trapped inside the rotating impeller, and as the solids to liquid ratio increases, the performance of the blending mixer may decline rapidly in operation. When sufficient loss of performance or erosion of the impeller occurs, in some cases, injection of the slurry into the well may decrease or cease, leading to interruption of a treatment operation in a subterranean formation penetrated by the wellbore. The same applies to the rotating slinger, as the performance of the blending mixer may decline rapidly in operation when the slinger becomes eroded.
There is a need for improved erosion and performance monitoring of continuously blending mixers which improves or overcomes difficulties due to damage to, and erosion of, rotating components, and such need is addressed, at least in part, by embodiments described in the following disclosure.